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Re: [Qemu-ppc] [PATCH v1 09/10] target-ppc: add vextu[bhw]lx instruction

From: Richard Henderson
Subject: Re: [Qemu-ppc] [PATCH v1 09/10] target-ppc: add vextu[bhw]lx instructions
Date: Thu, 24 Nov 2016 09:14:46 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 11/24/2016 06:53 AM, Nikunj A Dadhania wrote:
David Gibson <address@hidden> writes:

[ Unknown signature status ]
On Wed, Nov 23, 2016 at 05:07:18PM +0530, Nikunj A Dadhania wrote:
From: Avinesh Kumar <address@hidden>

vextublx:  Vector Extract Unsigned Byte Left
vextuhlx:  Vector Extract Unsigned Halfword Left
vextuwlx:  Vector Extract Unsigned Word Left

Signed-off-by: Avinesh Kumar <address@hidden>
Signed-off-by: Nikunj A Dadhania <address@hidden>

So, when I suggested doing these without helpers before, I had
forgotten that the non-byte versions can straddle the word boundary.
Given that the offset is in a register, not the instruction that does
make it complicated.

But, this version also relies on working 128-bit arithmetic, AFAICT
this will just fail to build if CONFIG_INT128 isn't defined.

It has both the implementation, just that the defines might have
confused you:


#  if defined(CONFIG_INT128)
#  else
#  endif

#else /* !defined (HOST_WORDS_BIGENDIAN) */

#  if defined(CONFIG_INT128)
#  else
#  endif


In include/qemu/int128.h, we do have int128_rshift. So you don't *really* have to do this by hand, exactly.


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